The other article, which appeared at the AES Energy Storage blog, was written by Praveen Kathpal, a vice president of AES Energy Storage. While the article mentions the help AES Energy Storage is providing in Puerto Rico, doing such things as helping clear roads and getting diesel fuel to a sewage authority, its central issue is the storage batteries in the Dominican Republic. AES installed them not all that long before the country was hit by Irma.
The two battery arrays were sited near Santo Domingo. They were intended to help maintain the AC power frequency. Each had a discharge capacity of 10 MW, but with only the ability to discharge at that rate for 30 minutes. While that might not sound like much, the battery systems were the equivalent of a much larger capacity of thermal plants, because they could respond to changes in demand instantly, instead of having to ramp up and down.
The most violent period of Irma’s onslaught lasted 10 hours. During that time, the batteries went through heavy use, both discharging and charging at rates far higher than normal. As the power grid was being battered, somewhere between 40% and 55% of the thermal plants were forced offline. Meanwhile, the transmission authority ordered the AES batteries to keep working. They did so under remote control from one of Dominicana’s thermal plant control rooms with an AES Energy Storage team monitoring them.